Radio communication apparatus

ABSTRACT

An AN (Access Network) controlled by a communication control apparatus and communicating with a AT Access Terminal), wherein the AN receives control information including information for allocating communication information from the communication control apparatus, and the AN transmits transmission cycle information for transmitting the communication information in a predetermined transmission cycle to the AT and allocates the communication information in the predetermined transmission cycle based on the control information received from the communication control apparatus to send the communication information to the AT.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 10/880,503, filedJul. 1, 2004. This application relates to and claims priority fromJapanese Patent Application No. 2004-116069, filed on Apr. 9, 2004. Theentirety of the contents and subject matter of all of the above isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a technique for controllingtransmission of communication information such as voice or data to betransmitted to an access terminal (which will be referred to as merelyAT, hereinafter) in a radio communication apparatus.

In a communication field, in these years, as broadband communicationspreads, routers and so on are technically advanced, and the need forend users to want to receive a large capacity of streaming video, etc.at ATs is increased; much attention has been focused on a technique forbroadcasting not only a large capacity of data or voice but also withuse of communication resources less than unicast communication, that is,a multicast technique. The multicast is a technique for simultaneouslytransmitting a single packet or a data stream to a plurality of parties.A router provided between a server and a client acts to copy the packetor the data stream by a necessary number and to transmit the copies to amultiplicity of ATs. The unicast, on the other hand, is a technique fortransmitting a plurality of packets or data streams to a plurality ofparties in a 1:1 relation. When the same voice or data is transmitted toa plurality of ATs, routers, servers, etc.; the employment of themulticast enables a traffic flowing through a network to be suppressedor the load of an application server to be reduced, when compared withthe unicast which requires transmission of a plurality of packets ordata streams.

Even in radio communication, for the purpose of realizing efficientradio bandwidth use, a communication technique for receiving a singlepiece of voice or data at a plurality of ATs has been studied.Conventionally, 1:1 unicast communication wherein a physical channel isallocated to each AT to establish a 1:1 radio communication connectionhas been employed. By allocating specific one of the physical channelsas a multicast channel, the same voice or data is transmitted to aplurality of ATs. That is, efficient radio bandwidth use can be realizedby receiving a single data stream at the plurality of ATs. The radiowave reception states at ATs vary depending on the radio wavepropagation environment between the AT and an access network (which willbe referred to merely as AN, hereinafter).

In the unicast communication, 1:1 communication is carried out betweenthe AT and the AN or sector. Thus, such adjustment can be possible as toincrease the data transmission rate of voice or data to be transmittedwhen the radio wave reception state of each AT is good or to decreasethe transmission rate when the wave reception state is bad. In themulticast communication, on the other hand, each AT is required toreceive voice or data transmitted at a specific data transmission ratefrom a prescribed multicast channel. Thus, there exists an AT whichcannot secure a bandwidth necessary for receiving data at thetransmission rate and cannot receive the multicast data due to bad radiowave reception environment. Whether or not the AT can decode thereceived voice or data depends on a ratio in magnitude between actuallyreceived voice or data and noise signals. In order for an increasednumber of ATs to be capable of receiving voice or data multicast with aconstant data transmission rate, it is required to increase the ratio inmagnitude of the actual voice or data signal to the noise signal.

When code division multiple access (CDMA) is used as the radiocommunication technique, communication is carried out by selecting oneof ANs (or sectors) which has the best radio wave state in theconventional unicast communication technique. For this reason, whenradio waves transmitted from adjacent ANs or sectors not selected havethe same frequency, the radio waves become all interference noise. As amethod for increasing the ratio of actual voice or data to noise, thereis described in 3GPP2 (3rd generation partnership project 2), C. S0054version 0.9 a technique wherein the same voice or data signals aretransmitted at the same timing from a plurality of adjacent ANs, andthese voice and data signals are combined at an AT. Since the same voiceor data signals are transmitted at the same timing from a plurality ofadjacent ANs or sectors and the signals transmitted from the ANs orsectors are combined at an AT, the ratio of actual voice or data tonoise can be made larger than that in the communication technique byselecting one of ANs (or sector) having a good radio wave environment.As a result, an increased number of ATs can receive the multicast data.The timing of transmitting voice or data from the ANs (or sectors) isincluded in control information and is informed from the ANs to the ATsat intervals of a constant period.

SUMMARY OF THE INVENTION

In a radio communication system, radio wave reception states of ATs varyaccording to their radio wave propagation environments. Thus the radiocommunication system requires a technique by which an increased numberof ATs can receive a voice or data signal multicast from ANs (orsectors) at an arbitrary data transmission rate. In this specification,a cluster of voice or data to be transmitted will be referred to asBCMCS (Broadcast/Multicast Service) flow, hereinafter. In a 1× EV-DO (1×Evolution Data Only) system for providing data communication based on aCDMA radio communication technique, a block called ECB (Error ControlBlock) having an error correction code applied to a data part isgenerated, the data part is divided into each BCMCS flows to betransmitted, and then transmitted. When a multicast service is carriedout in the 1×EV-DO system, for the purpose of enabling reception of theBCMCS flow at an increased number of ATs; voice or data signals from aplurality of ANs or sectors, which would be interference nose in theprior art, are transmitted at the same timing as the same voice or datasignal. To this end, the system is provided with a function of combiningand reconstructing the transmitted BCMCS flow. As a result, the radiowave propagation environments of the ATs can be improved. When a BCMCSflow becomes missed in a radio space, for the purpose of avoiding ashift in the timing of transmitting the BCMCS flow between ANs orsectors, the transmission/reception timing of the BCMCS flow isprescribed by an algorithm called ‘system time modulo transmissioncycle’. Since the transmission cycle of the entire BCMCS flows isprescribed by a sum value of transmission times of the respective BCMCSflows, the transmission cycle is dynamically changed by addition ordeletion of a BCMCS flow. When the transmission cycle varies, thetransmission/reception timing is changed. This results in that the ATcannot reconstruct the BCMCS flow being transmitted. For this reason,data or voice signal transmitted from the AN or sector is required to bediscarded in units of ECB. That is, in the prior art, since thetransmission cycle is changed by addition or deletion of a BCMCS flow,all the BCMCS flow being transmitted is affected thereby before andafter the addition or deletion of the BCMCS flow. In the multicastcommunication, since the same BCMCS flow is transmitted in synchronismbetween a plurality of ANs or sectors, the influence of the change inthe transmission timing is exerted upon the other ANs. For this reason,each time addition or deletion of a BCMCS flow is carried out at an AN(or sector), contents during listening thereto or viewing thereof isinterrupted for a constant time.

An object of the present invention is to provide an apparatus forrealizing such communication control that, even in the presence ofaddition or deletion of a BCMCS flow, a BCMCS flow transmitted from anAN can be reliably reconstructed at ATs.

In accordance with the present invention, the above object is attainedby an apparatus which includes a plurality of ATs and ANs fortransmitting and receiving data or voice to and from the ATs, and alsoincludes a means for finding a time at which the aforementionedcommunication information is transmitted to the ATs and a parameter fordefining a cycle of transmitting the aforementioned data or voicesignal, and a means for informing the ATs of the transmission time andthe parameter at a constant period on the basis of control information.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of a radio communication system 1 to whichthe present invention is applied;

FIG. 2 shows blocks having an error correction code applied to eachvoice or data to be transmitted to an AT 100-i;

FIG. 3 is a block diagram of a structure of a content distributionserver 104;

FIG. 4 shows a structure of a content storage database 302;

FIG. 5 is a block diagram showing an arrangement of a communicationcontrol apparatus 102;

FIG. 6 shows a structure of a database 512 provided in the communicationcontrol apparatus 102;

FIG. 7 shows a structure of a BCMCS flow management table 513 providedin the communication control apparatus 102;

FIG. 8 is a block diagram of a structure of an AN 101-i;

FIG. 9 shows a structure of a control information management table 812provided in the AN 101-i;

FIG. 10 is a flow chart for finding timing of transmitting a BCMCS flowin the communication control apparatus 102;

FIG. 11 is a flow chart for finding timing of transmitting a BCMCS flowin the communication control apparatus 102;

FIG. 12 is a sequence diagram showing the operation of the radiocommunication system 1 to which the present invention is applied;

FIG. 13 is a sequence diagram showing the operation of the radiocommunication system 1 to which the present invention is applied;

FIG. 14 is a sequence diagram showing the operation of the radiocommunication system 1 to which the present invention is applied;

FIG. 15 is a sequence diagram showing the operation of the radiocommunication system 1 to which the present invention is applied.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be detailed with reference tothe accompanying drawings.

1. Embodiment 1

FIG. 1 shows a configuration of a radio communication system 1 to whichthe present invention is applied. The radio communication system 1includes a plurality of ATs 100-i (i=1 to 3) to be connected with theATs, a plurality of ANs 101-i (i=1 and 2), and a communication controlapparatus 102 s connected to the plurality of ANs and a communicationnetwork 103. The communication network 103 is connected with a contentdistribution server 104.

The content distribution server 104 is a server for distributingcontents (communication information) such as voice or data to the ATs ona packet basis. A cluster of voice, data or the like distributed fromthe content distribution server 104 will be referred to as BCMCS flow,hereinafter.

The communication control apparatus 102 controls a physical data rateand an application data rate for each BCMCS flow. The apparatus finds atransmission time and transmission timing on the basis of the aboveinformation, and transmits the found information to the ANs 101-itogether with information about transmission cycle or the like.

The AN 101-i inserts the information about the transmission cycle,transmission time, transmission timing, etc. transmitted from thecommunication control apparatus 102 in control information 110, andinforms the AT 100-i of the information. The AN 101-i, on the basis ofthe control information about the transmission cycle, transmission time,transmission timing, etc.; also controls transmission of a BCMCS flow120 to the AT 100-i. As shown in FIG. 2, the AN 101-i further generatesblocks 200, 201, and 202 having an error correction code applied theretofor each voice or data to be transmitted to the AT 100-I; divides theblocks into BCMCS flow units each to be transmitted in one transmissioncycle 130; and then transmits each flow unit. The BCMCS flow isbroadcast and transmitted to the AT 100-i.

Each AT 100-i combines desired one of BCMCS flows (a_(i), b_(i), . . . ,and n_(i)) (e.g., i=1 to 9) transmitted from the plurality of ANs 101-1and 101-2, and reconstructs the desired BCMCS flow in units of block.For example, the AT 100-1 receives a block A (see FIG. 2) andreconstructs it. Similarly, the ATs 100-2 and 100-3 receive blocks B andC and reconstructs them respectively.

FIG. 3 is a block diagram of a configuration of a content distributionserver 104. The content distribution server 104 includes a processor300, a memory 301 for storing a program and so on to be executed by theprocessor 300, a content storage database 302 for storing contents to bedistributed to the ATs 100-i, and an input/output interface 303connected to the communication network 103.

FIG. 4 shows a structure of the content storage database 302. Stored inthe content storage database 302 are BCMCS flow IDs for identificationof contents and contents (such as movie, music, etc.) associatedtherewith. The processor 300 reads out the BCMCS flow ID and thecorresponding contents from the content storage database 302, convertsthem to packets, and transmits the packets from the input/outputinterface 303 to the communication network 103.

FIG. 5 is a block diagram of an arrangement of the communication controlapparatus 102. The communication control apparatus 102 has a lineinterface 500 to be connected to the ANs 101-i, a line interface 501 tobe connected to the communication network 103, a call control function502 connected to the line interfaces 500 and 501, and an apparatuscontroller 503 connected to the call control function 502.

In the illustrated example, the line interfaces 501 and 502 transmitsand receives a packet to and from the AN 101-i and the communicationnetwork 103, respectively. The call control function 502 in turn has aprocessor 510, a memory 511 for storing a program or the like to beexecuted by the processor 510, a database 512 for storing thetransmission rate, etc. of a BCMCS flow, and a BCMCS flow managementtable 513 for storing the transmission timing, etc. of the BCMCS flow.In the present embodiment, the processor 510 finds a BCMCS flow IDincluded in the packet received from the content distribution server 104and finds the transmission timing, etc. of the BCMCS flow from thedatabase 512; controls to transmit the found information to the AN101-i; and also records it in the BCMCS flow management table 513. Theapparatus controller 503 generally controls the entire communicationcontrol apparatus 102. A plurality of such line interfaces 500 may beprovided according to the number of ANs to be connected.

FIG. 6 shows a structure of the database 512 provided in thecommunication control apparatus 102. Stored in the database 512 are aBCMCS flow ID 601, a physical data rate 602 in a radio space when the AN101-i transmits a BCMCS flow to the AT 100-i, and an application datarate 603 required by an application of the AT 100-i, these data beingassociated with each other.

FIG. 7 shows a structure of the BCMCS flow management table 513 providedin the communication control apparatus 102.

Stored in the BCMCS flow management table 513 are a BCMCS flow ID 701for identification of the BCMCS flow, a transmission slot number 702, atransmission timing 703 (allocated head slot), and transmission cycle704, these data being associated with each other.

In the illustrated example, the transmission slot number 702 indicatesthe length of the BCMCS flow and is prescribed by the number of slots.The transmission timing 703 indicates timing of transmitting the BCMCSflow, and is prescribed by the position of the head slot on which thefirst unit of the BCMCS flow is to be allocated. The transmission cycle704 indicates a cycle (fixed value) at intervals of which the dividedBCMCS flow units are transmitted, and is prescribed by the number ofslots corresponding to the interval. The transmission cycle 704, whichis determined by a relation between the transmission rate of the BCMCSflow and delay, is previously set in the BCMCS flow management table513.

FIG. 8 is a block diagram of a structure of the AN 101-i. The AN 101-ihas a plurality of antennas 800-i (i=1 to 3), radio analog sections801-i (i=1 to 3) connected to the respective antennas 800-i, a digitalsignal processor 802 connected to the radio analog sections 801-i, aline interface 803 connected to the digital signal processor 802, a callcontrol function 804 connected to the digital signal processor 802 andthe line interface 803, and an AN controller 805 connected to the callcontrol function 804. The line interface 803 is connected also to thecommunication control apparatus 102.

In this example, the radio analog section 801-i converts an analogsignal received from the AT 100-i via the antenna 800-i into a digitalsignal, and outputs it to the digital signal processor 802. The radioanalog section 801-i converts the digital signal received from thedigital signal processor 802 into an analog signal, and transmits theconverted analog signal to the AT 100-i via the antenna 800-i. Thedigital signal processor 802 demodulates a signal received from theradio analog sections 801-i or modulates a signal to the AT 100-i. Theline interface 803 transmits or receives a packet to or from thecommunication control apparatus 102. The call control function 804 has aprocessor 810, a memory 811 for storing a program or the like to beexecuted by the processor 810, and a control information managementtable 812 for management of control information to be informed to theAT. The processor 810 also has a timer 820. The timer 820 is used totransmit a flow delete request of the BCMCS flow to the communicationcontrol apparatus 102, when the processor 810 fails to receive a view &listen request of the BCMCS flow from the AT 100-i for a predeterminedtime. Stored in the control information management table 812 areinformation on transmission timing, etc. of a BCMCS flow transmittedfrom the communication control apparatus 102. The processor 810transmits this information to the AT 100-i as control information.Though not illustrated, the AT stores the information informed by the ANin a memory provided in its own AT. The transmission period of thecontrol information is synchronized with the transmission cycle of theBCMCS flow (Equation (1)).

(one transmission period of control information)=n×(transmission cycleof one BCMCS flow), where n is a natural number  (1)

When the AT not communicating with the AN hands off between ANs, theinformation informed from the AN before hand-off and stored in thememory is updated to information informed from the AN after thehand-off. When the AT is not communicating with the AN, the AT isshifted to a sleep mode to suppress the consumption of a battery of itsown AT. In the sleep mode, the AT is activated about once in 5 seconds.Thus when the transmission period of the control information is notsynchronized with the transmission cycle of the BCMCS flow, a delaycorresponding to one transmission cycle at the most takes place afterreception of the informed information until the client watches andlistens to the BCMCS flow. Such a problem with the delay can be avoidedby synchronizing the transmission period of the control information withthe transmission cycle of the BCMCS flow.

On the basis of information about the transmission timing, etc. of theBCMCS flow, the processor 810 controls the transmission of the BCMCSflow to the AT 100-i. The AN controller 805 generally controls theentire AN 101-i.

FIG. 9 shows a structure of the control information management table 812provided in the AN 101-i. Stored in the control information managementtable 812 are a BCMCS flow ID 901 for identification of a BCMCS flowtransmitted from the communication control apparatus 102, a physicaldata rate 902, a transmission slot number 903, a transmission timing 904(allocated head slot), a transmission cycle 905, these data beingassociated with each other.

In this example, the physical data rate 902 indicates the transmissionrate of a BCMCS flow. The transmission slot number 903, which indicatesthe length of the BCMCS flow, is prescribed by the number of slots. Thetransmission timing 904, which indicates the timing of transmitting theBCMCS flow, is prescribed by the position of the head slot from whichthe BCMCS flow is allocated. The transmission cycle 905, which indicatesa cycle (fixed value) at which the divided BCMCS flow blocks aretransmitted, is prescribed by the number of slots.

FIGS. 10 and 11 show flow charts for finding timing of transmitting aBCMCS flow in the communication control apparatus 102. The value of thetransmission cycle previously found is previously set in the BCMCS flowmanagement table 513 of the communication control apparatus 102.

The processor 510 in the communication control apparatus 102 decides thepresence or absence of a modification in the BCMCS flow (step 1001). Inthe presence of a modification in the BCMCS flow, the processor 510decides whether the modification is a delete request of the BCMCS flowor an addition (new allocation) request of the BCMCS flow (step 1002).In the case of the BCMCS flow deletion request, the processor 510deletes information about the BCMCS flow in question from the BCMCS flowmanagement table 513 (step 1003). The processor 510 also transmits atransmission stop request of the BCMCS flow to the content distributionserver 104 (step 1004). Next, the processor 510 again determines thetransmission timing of the BCMCS flow (step 1005). At this time, inorder to realize effective use of idle slots, the processor 510determines the transmission timing of the existing BCMCS flow in such amanner that idle slots are concentratedly located at the last part ofthe transmission cycle as necessary. In other words, when the other ANis not transmitting a BCMCS flow during a period of the deleted BCMCSflow, the processor puts the BCMCS flow close to the preceding BCMCSflow. When the BCMCS flow is all deleted or when the deleted BCMCS flowis located at the last part of one transmission cycle, no modificationof the transmission timing is carried out. Next, when the processor 510determines the transmission timing of an existing BCMCS flow and thereis a modification in the transmission timing; the processor updates theBCMCS flow management table 513 (step 1006); or transmits information(BCMCS flow ID, physical data rate, transmission slot number,transmission timing, and transmission cycle) about the existing BCMCSflow to the AN 101-i (step 1007).

In the step 1002, if there is an addition request of the BCMCS flow,then the processor 510 searches the database 512 on the basis of theBCMCS flow ID included in the addition request (step 1111), andcalculates a transmission slot number necessary for transmitting theBCMCS flow in one transmission cycle on the basis of the correspondingphysical data rate and application data rate (step 1112). Subsequently,the processor 510 decides according to an equation (2) which follows,whether or not the BCMCS flow in question can be transmitted in onetransmission cycle (step 1113).

(transmission slot number of existing BCMCS flow)+(transmission slotnumber of addition BCMCS flow)≦=(transmission cycle)  (2)

When a sum of the transmission slot number of the existing BCMCS flowand the transmission slot number of the addition BCMCS flow is notlarger than the value of the transmission cycle according to equation(2); the processor 510 determines the timing of the addition BCMCS flow(step 1114); and adds information (BCMCS flow ID, physical data rate,transmission slot number, transmission timing, and transmission cycle)about the BCMCS flow in question in the BCMCS flow management table(step 1115). Requirements necessary for the addition of the BCMCS floware, as shown by equation (2), that the addition BCMCS flow have asufficient time to be allocated in one transmission cycle, and that asynchronization be established between the ANs in the allocated timezone of the addition BCMCS flow. The processor 510 transmits informationon the BCMCS flow to the AN 101-i (step 1116). In the step 1113, if asum of the transmission slot number of the existing BCMCS flow and thetransmission slot number of the addition BCMCS flow is larger than thevalue of the transmission cycle, then the processor 510 refuses theaddition of the BCMCS flow in question (step 1117).

FIGS. 12 to 15 show a sequence diagram showing the operation of theradio communication system 1 to which the present invention is applied.For the convenience of explanation, a relation,3(slots)=5(ms)(1(slot)≈1.67(ms)), is assumed to be satisfied. Thetransmission cycle of the BCMCS flow is set at 48 (slots) and ispreviously set in the BCMCS flow management table 513 in thecommunication control apparatus 102. In the present embodiment, withregard to each of BCMCS flows 1, 2, and 3; the physical data rate in theradio space between the AT and the AN and the request throughput of theapplication of the AT are previously registered in the database 512within the communication control apparatus 102 (refer to FIG. 6).

The data rate when 1,024 bits are transmitted in a time of 1 slot is614.4 kbits/s, the data rate when 1,024 bits are transmitted in a timeof 2 slots is 307.2 kbits/s, and the transmission rate when 1,024 bitsare transmitted in a time of 8 slots is 76.8 kbits/s. For thesimplification of explanation, data transmitted from the AN is assumedto be a cluster of raw data that is not having an encode part, anoverhead part applied thereto, etc. And in the initial state, it isassumed that any BCMCS flow is not transmitted yet from each AN 101-i.

First, the AT 100-i, for example, transmits periodically a view & listenrequest of the BCMCS flow 1 to the AN 101-i (step 1201).

The AN 101-i, when receiving the view & listen request of the BCMCS flow1, transmits an allocation request of the BCMCS flow to thecommunication control apparatus 102 (step 1202).

The communication control apparatus 102, when receiving the allocationrequest of the BCMCS flow 1, searches the database 512 on the basis of aBCMCS flow ID (1) included in the request (step 1203), and calculatesthe minimum number (12 slots) of transmission slots necessary fortransmitting the BCMCS flow in one transmission cycle (of 48 slots), onthe basis of the corresponding physical data rate (614.4 kbps) andapplication data rate (150 kbps) (step 1204). Next, the communicationcontrol apparatus 102 decides according to the above equation (2)whether or not the BCMCS flow can be transmitted in one transmissioncycle (of 48 slots). In this case, since the requirement of equation (2)is satisfied, the apparatus determines to allocate ones of the blocks ofthe BCMCS flow 1 of one transmission cycle (of 48 slots) corresponding12 slots from the head slot (step 1205). Subsequently, the communicationcontrol apparatus 102 adds information about the BCMCS flow ID (1),transmission slot number (12 slots), transmission timing (0 slots), andtransmission cycle (of 48 slots) (step 1206) to the BCMCS flowmanagement table (refer to FIG. 7); and also transmits these informationand information about the physical data rate (614.4 kbps) to the AN101-i (step 1207).

The AN 101-i, when receiving these information, adds the information tothe control information management table 812 (step 1208). Next, the AN101-i sets the BCMCS flow management timer 820 (step 1301) (see FIG.13), and transmits the received information to the AT 100-i at apredetermined period as control information (step 1302). On the basis ofthe above information, the AN 101-i then draws up a schedule to transmitthe BCMCS flow 1 from the content distribution server 104 to a pluralityof ATs 100-i in a broadcast manner in synchronism with the transmissioncycle of the control information (step 1303). The AN 101-i repeats itstransmitting operation in such a manner as to transmit a part of theBCMCS flow 1 corresponding to 12 slots and not to transmit datacorresponding to 36 slots (idle).

The AT 100-i, on the basis of the received control information, combinesand reconstructs BCMCS flows informed from the plurality of ANs 101-i.

It is assumed for example that the AT 100-i transmitted a view & listenrequest of the BCMCS flow 2 to the AN 101-i (step 1304). In this case,as in the steps 1202 to 1208 (see FIG. 12), 1301, and 1302; the BCMCSflow 2 is allocated. As shown in FIG. 7, the minimum number oftransmission slots necessary for the BCMCS flow 2 is 10, and thetransmission timing (allocated head slot) is slot 12. In this case,since the BCMCS flow 1 is allocated from the head slot (0) within onetransmission cycle and transmitted, the BCMCS flow 2 is allocated by anamount corresponding to 10 slots immediately after the allocation of theBCMCS flow 1. A state of a BCMCS flow transmitted from the AN 101-i isshown by reference numeral 1350. The AN 101-i transmits the BCMCS flow 1by 12 slots, and transits the BCMCS flow 2 by 10 slots, and does nottransmit data corresponding to 26 slots (idle), which operations arerepeated.

Even when the AT 100-i transmits a view & listen request of the BCMCSflow 3, the BCMCS flow 3 is allocated, as in the steps 1202 to 1208 (seeFIG. 12), 1301, and 1302 (see FIG. 13). As shown in FIG. 7, the minimumnumber of transmission slots necessary for transmitting the BCMCS flow 3is 8, and the transmission timing (allocated head slot) is slot 22. Inthis case, since the physical data rate in the radio space is 76.8 kbpsand the request data rate is 5 kbps, the transmission slot numberbecomes 4 at the minimum by calculation. Since the radio space physicaldata rate of 76.8 kbps is prescribed as a data rate when data of 1,024bits is transmitted using 8 slots, however, the number of allocatedslots is required to be a multiple of 8. Thus, the minimum number ofslots is not 4 but 8. Since the BCMCS flows 1 and 2 are allocated fromthe head slot (0) in one transmission cycle and transmitted, the BCMCSflow 3 is allocated immediately after the allocation of the BCMCS flow2. A state of a BCMCS flow transmitted from the AN 101-i is shown byreference numeral 1450 (see FIG. 14). The AN 101-i transmits the BCMCSflow 1 by 12 slots, transmits the BCMCS flow 2 by 10 slots, transmitsthe BCMCS flow 3 by 8 slots, and does not transmit data corresponding to16 slots (idle). The AN repeats the aforementioned operations.

Next, when the AN 101-i fails to receive the view & listen request ofthe BCMCS flow 1 from the AT 100-i for a time set by the BCMCS flowmanagement timer 320, the AN decides that there is no AT which islistening to the BCMCS flow 1 in an area covered by its own AN (step1501), and transmits a deletion request of the BCMCS flow 1 to thecommunication control apparatus 102 (step 1502).

The communication control apparatus 102, when receiving the deletionrequest of the BCMCS flow 1, confirms that the other ANs are nottransmitting the BCMCS flow 1, and then deletes information about BCMCSflow 1 from the BCMCS flow management table 513 (step 1503). Thecommunication control apparatus 102 also transmits a transmission stoprequest of the BCMCS flow 1 to the content distribution server 104 (step1504). The communication control apparatus 102 then again determines thetransmission timing of the existing BCMCS flows 2 and 3 (step 1505), andupdates the BCMCS flow management table 513 (step 1506). Since the BCMCSflow 1 allocated from the head slot becomes now null, the allocatedposition of the BCMCS flows 2 and 3 in one transmission cycle isforwardly shifted. The communication control apparatus 102 alsotransmits information (BCMCS flow ID, physical data rate, transmissionslot number, transmission timing, and transmission cycle) about theBCMCS flows 2 and 3 to the AN 101-i (step 1507).

The AN 101-i, when receiving the information on the BCMCS flow 2 and 3,updates the database 512 (step 1508). The AN also the information of theBCMCS flows 2 and 3 to the AT 100-i as control information at intervalsof a predetermined period (step 1509). Next, the AN 101-i, on the basisof the above information, draws up a schedule to transmit the BCMCSflows 2 and 3 from the content distribution server 104 to a plurality ofATs 100-i in a broadcast manner in synchronism with the transmissionperiod of the control information (step 1510).

On the basis of the received control information, the AT 100-i combinesand reconstructs BCMCS flows informed from the plurality of ANs 101-i.

As has been explained above, in accordance with the present invention,since communication information to be transmitted to the AT is set to betransmitted thereto at constant intervals of a predetermined cycle, theBCMCS flow transmitted from the AN can be reliably reconstructed at theAT.

In Embodiment 1, parameters of the transmission slot number,transmission timing, and transmission cycle have been prescribed by thenumber of slots or the slot number (refer to FIGS. 7 and 9). However,such parameters may be prescribed by time.

Although the BCMCS flow monitoring timer has been provided in the AN101-i in embodiment 1, the timer may be provided in the communicationcontrol apparatus 102.

In Embodiment 1, further, parameters such as the transmission slotnumber, transmission timing, etc. of the BCMCS flow have been found bythe communication control apparatus 102 in Embodiment 1. However, thedatabase 512 and the BCMCS flow management table 513 may be provided ineach AN and each AN may find such parameters.

2. Embodiment 2

The transmission cycle parameters have been set for control inEmbodiment 1. However, the problem can also be avoided by fixing all thetransmission times of respective BCMCS flows to a least common multipleγ of the transmission times for prescribed standard data rates.

Since the transmission time of the BCMCS flow in one transmission cycleis fixed to the least common multiple value γ of the transmission timesfor prescribed standard data rates, the BCMCS flow of all the prescribedstandard data rates can be allocated to the fixed transmission time. Thevalue γ is set as a parameter in the AN or the communication controlapparatus.

The number of BCMCS flows to be transmitted in one transmission cycle isprescribed as a parameter of an allowable maximum BCMCS flow number ηand similarly set. Using the above two parameters, the transmissioncycle of the BCMCS flow is expressed by “γ×η”.

In accordance with the present invention, the transmission cycle can bekept constant even before or after the addition or deletion of a BCMCSflow, the addition or deletion of the BCMCS flow enables thetransmission cycle to be changed, whereby the problem that thisinfluences the other BCMCS flows, can be avoided.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An AN (Access Network) controlled by a communication controlapparatus and communicating with a AT Access Terminal), wherein the ANreceives control information including information for allocatingcommunication information from the communication control apparatus, andthe AN transmits transmission cycle information for transmitting thecommunication information in a predetermined transmission cycle to theAT and allocates the communication information in the predeterminedtransmission cycle based on the control information received from thecommunication control apparatus to send the communication information tothe AT.
 2. The AN according to claim 1, wherein the transmission cycleinformation is received from the communication control apparatus.
 3. TheAN according to claim 1, wherein the communication information which isallocated and sent in the predetermined transmission cycle is requiredby the AT.
 4. The AN according to claim 1, wherein the information forallocating the communication information includes a transmission slotnumber indicating a length of the communication information and atransmission timing indicating a period in the predetermined cycleallocated for the communication information.
 5. The AN according toclaim 1, wherein, if the AN needs not to transmit any of plural piecesof the communication information to the AT, the AN pads a periodallocated for the piece of the communication information not to betransmitted with the communication information which is allocated in thenext period.
 6. An AN controlled by a communication control apparatusand communicating with a plurality of AT(Access Terminal)s, wherein theAN receives control information including information for multiplexingcommunication information from the communication control apparatus, andthe AN transmits transmission cycle information for transmitting thecommunication information in a predetermined transmission cycle to theATs and multiplexes the communication information in the predeterminedtransmission cycle based on the control information received from thecommunication control apparatus to send it to the ATs.
 7. The ANaccording to claim 6, wherein the transmission cycle information isreceived from the communication control apparatus.
 8. The AN accordingto claim 6, wherein the communication information which is multiplexedand sent in the predetermined transmission cycle is required by the ATs.9. The AN according to claim 6, wherein the information for multiplexingthe communication information includes a transmission slot numberindicating a length of the communication information and a transmissiontiming indicating a period in the predetermined cycle allocated for thecommunication information.
 10. The AN according to claim 6, wherein, ifthe AN needs not to transmit any of plural pieces of the communicationinformation to the ATs, the AN pads a period allocated for the piece ofthe communication information not to be transmitted with thecommunication information which is allocated in the next period.
 11. AnAT communicating with an controlled by a communication controlapparatus, wherein the AT receives control information including apredetermined transmission cycle, a transmission slot number indicatinga length of communication information, and a transmission timingindicating a period allocated for the communication information in thepredetermined transmission cycle, and the AT extracts the communicationinformation specified by the transmission slot number and thetransmission timing in the control information from plural piece ofcommunication information allocated in the predetermined cycle and sentfrom the AN to receive the extracted communication information.
 12. AnAT communicating with an controlled by a communication controlapparatus, wherein the AT receives control information including apredetermined transmission cycle, a transmission slot number indicatinga length of communication information, and a transmission timingindicating a period allocated for the communication information in thepredetermined transmission cycle, and the AT extracts the communicationinformation specified by the transmission slot number and thetransmission timing in the control information from plural piece ofcommunication information multiplexed in the predetermined cycle andsent from the AN to receive the extracted communication information. 13.A radio communication method performed by an AN wirelessly communicatingwith an AT and a communication control apparatus controlling the AN,comprising the steps of: sending, by the communication controlapparatus, transmission cycle information and control information to theAN, the transmission cycle information being for transmittingcommunication information to the AT in a predetermined transmissioncycle and the control information including information for allocatingthe communication information; sending, by the AN, the transmissioncycle information received from the communication control apparatus tothe AT; and allocating, by the AN, the communication information basedon the control information received from the communication controlapparatus and sends it in the predetermined transmission cycle to theAT.
 14. The radio communication method according to claim 13, whereinthe communication information which is allocated and sent in thepredetermined transmission cycle is information required by the AT. 15.The radio communication method according to claim 13, wherein theinformation for allocating the communication information includes atransmission slot number indicating a length of the communicationinformation and a transmission timing indicating a period in thepredetermined cycle allocated for the communication information.
 16. Theradio communication method according to claim 13, further including thestep of calculating, by the communication control apparatus, atransmission slot number necessary for transmitting the communicationinformation in the predetermined transmission cycle based on a physicaldata rate and an application data rate corresponding to thecommunication information included in a transmission request from the ATto determine a transmission timing indicating a period in thepredetermined cycle allocated for the communication information.
 17. Theradio communication method according to claim 13, further including thestep of, if the AN needs not to transmit any of plural pieces of thecommunication information to the AT, padding, by the AN, a periodallocated for the piece of the communication information not to betransmitted with the communication information which is allocated in thenext period.
 18. A radio communication method performed by an AN forwirelessly communicating with a plurality of ATs and a communicationcontrol apparatus controlling the AN, comprising the steps of: sending,by the communication control apparatus, transmission cycle informationand control information to the AN, the transmission cycle informationbeing for transmitting communication information to the ATs in apredetermined transmission cycle and the control information includinginformation for multiplexing the communication information; sending, bythe AN, the transmission cycle information received from thecommunication control apparatus to the ATs; and multiplexing, by the AN,the communication information in the predetermined transmission cyclebased on the control information received from the communication controlapparatus to send it to the ATs.
 19. The radio communication methodaccording to claim 18, wherein the communication information which ismultiplexed in the predetermined transmission cycle is informationrequired by the AT.
 20. The radio communication method according toclaim 18, wherein the information for multiplexing the communicationinformation includes a transmission slot number indicating a length ofthe communication information and a transmission timing indicating aperiod in the predetermined cycle allocated for the communicationinformation.
 21. The radio communication method according to claim 18,further including the step of calculating, by the communication controlapparatus, a transmission slot number necessary for transmitting thecommunication information in the predetermined transmission cycle basedon a physical data rate and an application data rate corresponding tothe communication information included in a transmission request fromthe AT to determine a transmission timing indicating a period in thepredetermined cycle allocated for the communication information.
 22. Aradio communication method according to claim 18, further including thestep of, if the AN needs not to transmit any of plural pieces of thecommunication information to the ATs, padding, by the AN, a periodallocated for the piece of the communication information not to betransmitted with the communication information which is allocated in thenext period.
 23. An AN controlled by a communication control apparatusand communicating with a AT, wherein the AN fixes a transmission timefor each piece of communication information to a least common multiple γof transmission times corresponding to data rates defined for respectivepieces of communication information, prescribes a number of pieces ofcommunication information transmitted in one transmission cycle as anallowable maximum number η, and transmits the communication informationto the AT based on a transmission cycle information set with γ×η.
 24. Aradio communication method performed by an AN controlled by acommunication control apparatus and communicating with an AT, includingthe steps of: fixing a transmission time for each piece of communicationinformation to a least common multiple γ of transmission timescorresponding to data rates defined for respective pieces ofcommunication information; prescribing a number of pieces ofcommunication information transmitted in one transmission cycle as anallowable maximum number η; and transmitting the communicationinformation to the AT based on a transmission cycle information set withγ×η.